Using a Snow Drift Model to Simulate Eolian Drift and Snowfall on the Summit of Mauna Kea, Hawaii

Abstract

The goal of this research is to help develop a better understanding of the micro-meteorology of the Mauna Kea summit area and its relationship to the distribution and population health of the Wēkiu bug (Nysius wekiuicola). SnowModel, a spatially distributed snow-evolution model, is used to construct snowfall and summit eolian debris (known as bug fall throughout this study) accumulation maps across the summit. Eight weather stations associated with astronomical observatories on the summit ridges and four Davis weather stations located in various cinder cones (pu‘u in Hawaiian), provide the meteorological observations needed as input to run SnowModel. Snow depth observations taken after a passing cold front in January 2011 are used to help validate the model accumulation predictions prior to the climatological study. Observations from summit weather stations over a three-year period (2008, 2009, and 2010) are used as input for the modeled summit accumulations of snowfall and bug fall presented in this study. For the snowfall maps, only weather data from days during which snow fell are included. For the bug-fall estimates, all days where valid weather data are available are included in the model output. Since there are no comprehensive data available on the distribution of bug fall, the bug-fall maps only provide a climatological pattern, without reference to the magnitude of the bug fall. The greatest modeled snow accumulations are found on Pu‘u Wēkiu and Pu‘u Haukea. Similar results are found in the climatological bug-fall accumulation pattern. Prevailing wind direction is most critical for the distribution of snowfall and bug fall, with maximum accumulations occurring on the lee side of ridges and crests. Favorable Wēkiu bug trapping sites in which bugs were found historically are spatially well collocated with snowfall and bug-fall accumulations, suggesting that the results of this study will be of interest to entomologists in locating Wēkiu bug populations.